Old Doran Smith 3871 mcb and how to determine type and Zs

[franksko]

Hi electricians,
can any one let me know how you can tell which type the old doran smith 3871 mcbs are as I can,t see a 1 ,2, or c or three on em? and what is the max Zs value for them as I can,t see it in the regs? so how can you know whether they are within the disconnection times permitted by current BS7672 2008? Help please?
PS I have the 80% values from G3 but they are useless if you can,t determine which relevant type you are dealing with? and would they still be applicable now anyway? Frank

 

[Pensdown]

BS 7672 - Specification for compression, stiffness and labelling of anti-embolism hosiery

Surgical stockings, Stockings, Hosiery, Medical equipment, Compression loading, Compression testing, Mechanical testing, Stiffness, Marking, Test equipment, Testing conditions, Calibration, Specimen preparation.

Are you sure you're in the right forum?

 

[ericmark]

3871 is the old British standard for MCB's so BS 3871 does not tell anyone what type of MCB it is. I looked at http://www.beamainstallation.org.uk/assets/pdfs/CircuitBreaker.pdf which explains how the standards evolved.
The Dorman Smith Loadmaster was very common years ago and because not a din rail mount very hard to replace without whole enclosure replacement but I seem to remember there was only a thermal trip in them and not a magnetic type as well so they would not have a number or letter just a current rating.
Originally there would have been a graph like we still get for a fuse and I would not think they would comply with BS7671:2008 and will need replacing to comply. Not sure what I would code it as? I think Code 2 "(Requires improvement) This code is to be used to indicate that the observed deficiency requires action to remove potential danger.
The person ordering the report should be advised that, whilst the safety of those using the installation may not be at immediate risk, remedial action
should be taken as soon as possible to improve the safety of the installation." would be appropriate but maybe your not talking about the LoadMaster
Eric

 

[franksko]

many thanks for the info ericmark, a code 2 would seem the right thing to do. interesting about the thermal trip. and some of the breakers have had the rating rubbed off due to wear and tear as they are very old.
Along with not knowing the rating on some of the breakers and what catagory of type? to reference em and the old DB not able to take a current sorry bout that breaker, I am in a bit of a pickle on this but your info is very much appreciated and once again thank you ericmark
franksko